1. Technical Field
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus. More specifically, the present invention relates to an ink jet type recording head and ink jet type recording apparatus which discharges ink as liquid.
2. Related Art
One ink jet type recording head of a liquid ejecting head currently known in the art uses an actuator having a vibration-mode piezoelectric element. The piezoelectric elements vibrates a vibration plate disposed adjacent to a pressure generating chamber communicating with a nozzle opening causing pressure to be applied to the ink in the pressure generating chamber such that ink droplets are discharged from the nozzle opening.
The ink jet recording head includes a passage forming substrate communicating with the nozzle opening. The passage forming substrate has a plurality of pressure generating chambers which are arranged in parallel and are partitioned by partition walls, a piezoelectric element which is formed by stacking a lower electrode membrane, a piezoelectric layer, and an upper electrode membrane with an insulating membrane disposed between the piezoelectric element and the pressure generating chamber of the passage forming substrate. The insulating membrane functions as a vibration plate, while a reservoir forming substrate includes a reservoir portion which is adhered to the passage forming substrate serves as a common ink chamber of the pressure generating chamber. An example of such a configuration is shown in Japanese Patent Document JP-A-2007-26125.
An ink supply path for supplying ink in the reservoir portion to the respective pressure generating chamber is provided to the respective pressure generating chamber. The respective ink supply paths are formed by extending the partition walls disposed at both sides of width direction of the respective pressure generating chamber. Furthermore, an upper surface of each partition wall is adhered to a reservoir forming substrate with the vibration plate formed there between, and an under surface of each partition wall is adhered to a nozzle plate.
One problem with the ink jet type recording head according to this configuration, however, is that the difference in the linear expansion coefficient between the passage forming substrate and the nozzle plate causes bending stress over the whole passage forming substrate. This stress is particularly strong at one of the weakest areas of the passage forming substrate, near the end portion of the partition walls of the ink supply path. The stress may result in breaks and damaged recording heads.
Also, the bending stress that causes a surface of the nozzle plate to become concave, causing increased stress as the partition wall is pulled by the nozzle plate, and as a result, the vibration plate may become cracked and broken.
As mentioned above, the vicinities of end portions of the partition walls partitioning the pressure generating chambers are apt to be broken by the bending stress, so that the quality and performance of the ink jet recording head may be deteriorated. This difficulty exists not only in the ink jet type recording head discharging ink but also in other liquid ejecting heads discharging liquid other than ink.